Mendelian Genetics Chapter 11 Section 3

Independent Assortment Mendel performed an experiment to follow two different genes as they passed from one generation to the next He found out: Law of Independent Assortment

Two-Factor Cross: F1 Mendel crossed plants that were homozygous dominant for round yellow peas with plants that were homozygous recessive for wrinkled green peas. (RRYY x rryy)

Two-Factor Cross: F2 Mendel crossed two F1 generation plants (heterozygous round yellow pea plants RrYy)

Law of Independent Assortment Mendel’s experiment showed that the alleles for seed shape and seed color in pea plants segregated independently One trait does not influence the other’s inheritance

Summary of Mendel’s Principles 1) The inheritance of traits is determined by genes. Genes are passed from parents to offspring. 2) In cases in which two or more alleles of the gene for a single trait exist, some may be dominant while others recessive

Summary of Mendel’s Principles 3) In most sexually reproducing organisms, each adult has two copies of each gene---one from each parent. These genes are segregated from each other when gametes form. 4) The alleles for different genes usually segregate independently of one another.

Incomplete Dominance What happens when you cross a red flowered plant with a white flowered plant? Result: Neither white nor red are dominant or recessive Incomplete Dominance: Case where one allele is not completely dominant over another

Incomplete Dominance

Codominance Codominance occurs when both alleles contribute to the phenotype

Multiple Alleles Many genes have more than two alleles and are therefore said to have multiple alleles. Example: Blood Typing